The present invention relates to printers and to memories for printers. More particularly, the invention relates to a robust bit scheme for a memory of a replaceable printer component.
The art of inkjet technology is relatively well developed. Commercial products such as computer printers, graphics plotters, and facsimile machines have been implemented with inkjet technology for producing printed media. Generally, an inkjet image is formed pursuant to precise placement on a print medium of ink drops emitted by an ink drop generating device known as an inkjet printhead assembly. An inkjet printhead assembly includes at least one printhead. Typically, an inkjet printhead assembly is supported on a movable carriage that traverses over the surface of the print medium and is controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to a pattern of pixels of the image being printed.
Inkjet printers have at least one ink supply. An ink supply includes an ink container having an ink reservoir. The ink supply can be housed together with the inkjet printhead assembly in an inkjet cartridge or pen, or can be housed separately. When the ink supply is housed separately from the inkjet printhead assembly, users can replace the ink supply without replacing the inkjet printhead assembly. The inkjet printhead assembly is then replaced at or near the end of the printhead life, and not when the ink supply is replaced.
Current printer systems typically include one or more replaceable printer components, including inkjet cartridges, inkjet printhead assemblies, and ink supplies. Some existing systems provide these replaceable printer components with on-board memory to communicate information to a printer about the replaceable component. The on-board memory, for an inkjet cartridge for example, may store information such as pen type, unique pen code, ink fill level, marketing information, as well as other information. Such a memory may also store other information about the ink container, such as current ink level information. The ink level information can be transmitted to the printer to indicate the amount of ink remaining. A user can observe the ink level information and anticipate the need for replacing a depleted ink container.
If the data received by a printer from a printer component memory contains an error, the printer may perform an incorrect action, or may be unable to use the printer component. Such an error may be the result of a short circuit or open circuit in an address line coupling the memory to other printer components, such as a printer controller, or from some other problem.
It is desirable to have a memory scheme that is more robust than current memory schemes used in replaceable printer components to detect and correct errors and provide uninterrupted operation.
One aspect of the present invention provides a method for detecting an error in data received from a memory of a replaceable printer component. The memory includes a plurality of bits. The method includes providing a first parity bit associated with a first data item. The first data item and the first parity bit are stored in the printer memory. The printer includes a plurality of electrically conductive lines. At least one of the electrically conductive lines is associated with each bit. The first data item and the first parity bit are read from the memory. An electrical test of at least one of the electrically conductive lines is performed. An error in the first data item is identified based on the first parity bit read from the memory and the electrical test.
One aspect of the invention is directed to a printing system including a printhead for selectively depositing ink drops on print media. An ink supply stores ink to be provided to the printhead. A memory device stores a first parity bit and a first data item. The first parity bit is associated with the first data item. A processor is coupled to the memory device by a plurality of electrically conductive lines. The processor is responsive to output of the memory device. The processor performs an electrical test of at least one of the electrically conductive lines. The processor identifies an error in the first data item based on the first parity bit and the electrical test.
Another aspect of the invention is directed to a cartridge for a printing system having a controller. The cartridge includes a printhead assembly having at least one printhead that selectively deposits ink drops on print media. An ink supply stores ink to be provided to the printhead. An information storage device stores a first parity bit and a first data item. The first parity bit is associated with the first data item. The first parity bit is used by the controller in conjunction with an electrical test of electrically conductive lines coupled to the information storage device to identify an error in the first data item.
Another aspect of the invention is directed to a replaceable printer component having an integral memory for use in a printing system. The component includes a semiconductor die and a plurality of circuits formed on the semiconductor die. Each circuit is associated with and indicates the state of a bit in the memory. The memory stores a plurality of functional bits that must match values expected by the printing system for proper operation of the printing system. The memory stores a plurality of informational bits that are not critical to proper operation of the printing system. A large percentage of the circuits associated with the functional bits are positioned substantially near a center of the semiconductor die. A large percentage of the circuits associated with the informational bits are positioned substantially outside of the center of the semiconductor die.
Another aspect of the invention is directed to a method of storing information in a replaceable printer component having an integral memory. The replaceable printer component is employed in a printing system. The method includes providing a semiconductor die with a plurality of circuits formed on the semiconductor die. Each circuit is associated with and indicates the state of a bit in the memory. The method includes identifying functional bit fields related to the replaceable printer component that must match values expected by the printing system for proper operation of the printing system. The method includes identifying informational bit fields related to the replaceable printer component that are not critical to the proper operation of the printing system. The method includes storing a large percentage of the functional bit fields in the semiconductor die using circuits that are positioned substantially near a center of the semiconductor die and storing a large percentage of the functional bit fields in the semiconductor die using circuits that are positioned substantially near a center of the semiconductor die.